Assessing the efficacy of five commonly used snake and gecko repelling agents when applied outdoors

Abstract

Human-snake conflict is increasing because of human expansion. Snakebite envenomation is a neglected disease that accounts for morbidity, mortality, and economic hardship. The effects of snakebite envenomation are most severe in the developing countries of Africa, Asia, Latin America, and Papua New Guinea. The World Health Organization has resolved to address this issue through improved access to and availability of crucial medical care. Prevention of snake-bite envenomation, however, is better than cure. Snake repellents are often used and conse-quently, there is a lucrative market for such products. In South Africa, there are also a variety of “home remedies” believed to repel snakes. The most often cited to be used are geraniums (including Pelargonium spp.), Jeyes Fluid, Condy’s crystals and naphthalene (moth balls). There is also a commercial product called Snake Repel, available in South African retail stores. Despite the widespread use of these agents, no study has assessed the in-field repulsion effi-cacy or chemical persistence of these agents. This thesis presents the first known effort to ad-dress this in the field. Snakes and other reptiles were passively trapped in drift fence funnel trap arrays, while in their natural movement. Sampling was carried out in northern Limpopo Province from December 2018 to February 2019. The effect of the repellents on reptile, snake and lizard abundance and species was assessed using nested analyses of variance. The effect of the repellents on the reptile, snake and lizard community was also assessed using non-metric multidimensional scaling. None of the agents tested displayed greater in-field repulsion efficacy compared to the control, water. This lack of repulsion was evident at both the spe-cies-and community level. Reptile activity levels displayed temporal variation in accordance with their ectothermic nature. The chemical persistence of the agents was also investigated using gas chromatography-mass spectrometry (GC-MS). Jeyes Fluid Original, Snake Repel and naphthalene demonstrated rapid, continuous decay of initial volatile chemical compound concentrations, which is undesirable in a snake-repelling agent. The rapid dispersion of any potentially snake-repelling volatiles in these supposed remedies would reduce the likelihood of snakes detecting the volatiles and therefore lead to decreased repulsion efficacy. The lack of in-field repulsion efficacy and low chemical persistence displayed by the agents tested in this study indicate that no known traditional or commercial products effectively repel snakes. Thus, alternative methods of snakebite management should be investigated.